Hello Guys,
Before installing ISPConfig i made a manual setup of Nginx with reverse proxy to Apache2 and then I've tried running Varnish cache in front of both Nginx and Apache2 servers.
this setup were suprisingly very fast, page loading time decreased from around 5 Seconds to 2 Seconds (if site got cached with Varnished)

and it also give a really favorable results with WordPress sites as the main idea is: that when you browse your site it should be going with nginx and Varnish and only reaching Apache if the content is not cached or if user is on the WP-admin page or when calling post requests.
and with benchmark and site stress testing , the results were great with doubling the spead,decreasing the loading time and the handling of traffic. without calling much of Nginx workers and Apache-MPM processes (using cache when available).

Now after doing a clean server setup to install ISPConfig with only Nginx, i am having a trouble to make this setup again as the sites should be hosted with Apache and i made Nginx install with ISPConfig and of course i want to make the whole environment running with only ISPConfig without referring to manual modifications, so i think there is only one choice, which is:

Converting ISPConfig to work with Apache.

so how could i achieve such a thing without reinstalling the whole Control Panel and messing the sites.